a String Length Function without using <cstring>

[TheIdeasMan]

@Z feng

No need to be sorry, everyone starts somewhere, and we are pleased to help out. :-D

xhtmlx wrote:

He wouldn't be able to return i if he removed that.

Why not ? What is wrong with this:

int myStrLen(const char str[])
{
int i = 0;
for(int i = 0; str[i] != '\0'; i++)   ;
return i;
}

Edit removed the semicolon.

Edit 2: I am still mystified why one would want to count the null character.

[TheIdeasMan]

I code my loops like this, so to avoid the annoying & hard to see extra semicolon:

for(int i = 0; str[i] != '\0'; i++) {
    return i;}

I do this even if there is only 1 statement in the loop, it might save me or you one day, if more code is added.

[DesiredNote]

for(int i = 0; str[i] != '\0'; i++) {
    return i;
}

That code would return 0 and then exit the function. None of the characters would have been counted, nor would i even be increment. That's why I added a null-statement to the for loop and move i out of the scope.

[TheIdeasMan]

OK, I am going mad in my old age !!!

I see what you have done (and I see about the scope), although I would say that if you are going to use a null statement, then do it like this with the comment, so that everyone can see that you have done it on purpose:

int myStrLen(const char str[])
{
int i = 0;
for(int i = 0; str[i] != '\0'; i++)   
           ; // null statement
    return i;
}

Otherwise people might easily think it as an error.

I came up with this:

int i;
	for( i = 0; str[i] != '\0'; /*no increment*/) {
		i++;}
		return i;

One can now see why K&R had a while statement. While loops are better if the limit is not a known value.

Any way we have now had 2 days of discussion about the strlen function !!! Given it a thorough bashing I think.

I need a beer !!!

[Z feng]

Thank you TheIdealMan, could you tell me the big difference between them? i thought they were basicly same...

[TheIdeasMan]

Well one can be written as the other - they are interchangeable in that respect.

Psuedo Code

begin initialise
while(end condition) {
// do stuff
increment expression
}

for(initialise;end condition;increment){
//do stuff
}

As I said, while loops are better if the end condition or limit is not a known value. For example with strings or files, the length isn't known, so use a while loop. That is what Kernighan & Ritchie (K&R the inventors of the C Language) have done. You can see how the while is easier to understand in the strlen example. The for loop has null statements or missing increment expression. The only thing about the K&R example is they didn't initialise the counter to zero because it is an automatic variable - meaning that it is automatically initialised to zero. However, common practice these days is to initialise nearly everything regardless. Lack of initialisation is one of the most common errors, especially for newbies.

Hope this is all sorted out now.

[Z feng]

get it! Thank you so much!